[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/POLITICS/07/11/obama.netroots/art.obama.va.gi.jpg caption="Sen. Barack Obama said he voted for the surveillance bill because it will help protect the nation."]
WASHINGTON (CNN) - Sen. Barack Obama's vote for a federal surveillance law that he had previously opposed has sparked a backlash from his online advocates, who had energized his campaign for the Democratic presidential nomination.
In October, Obama had vowed to help filibuster an update of the Foreign Intelligence Surveillance Act (FISA) that gave telecommunication companies that had cooperated with President Bush's warrantless wiretapping program immunity from lawsuits.
After 9/11, Bush secretly authorized the National Security Agency to eavesdrop, without the mandated warrant from a federal court, on electronic communication involving terrorist suspects.
Critics said Bush's Terrorist Surveillance Program was a violation of civil liberties.
The Senate voted Wednesday on the bill updating FISA - which had a provision to shield telecommunications companies that had cooperated in the surveillance. Obama joined the 68 other senators who voted to send the bill to the president's desk.